Various known devices can be used to increase the power output of an internal combustion engine during operation of an associated vehicle by increasing, or pressurizing, the airflow to a fuel system component which supplies a flammable fuel/air mixture to the engine. One device of this type can be used on a motorcycle having an internal combustion engine, with the device including a housing and a pair of rotatable butterfly valves connected to the housing. The airflow to a fuel system component can be varied during operation of the motorcycle by rotating the butterfly valves. While devices of this type have been used successfully, they can be subject to certain disadvantages. For example, the butterfly valves are always exposed to the air stream during operation of the motorcycle. During operation in inclement weather, for example rain, this can result in the undesirable introduction of excess moisture in the air supplied to the fuel system component which in turn can cause undesirable engine hydrolock. This can be especially undesirable in ram air or hypercharger systems.